Mercury switch with alignment responsive means



P. L. BETZ Jan. 22, 1952 MERCURY SWITCH WITH ALIGNMENT RESPONSIVE MEANS Filed Jlily 22, 1948 Patented Jan. 22, 1952 MERCURY SWITCH WITH ALIGNMENT RESPONSIVE MEANS Paul L. Betz, Baltimore, Md., assignor to Consolldated Gas Electric Light and Power Company of Baltimore, Baltimore, Md., a corporation Maryland Application July 22, 1948, Serial No. 40,123

5 Claims.

This invention relates to mercury switches of the tiltable container type, and more particularly to such mercury switches provided with means whereby they can be energized only when properly installed.

Mercury switches of the type employing a tiltably mounted container, such as a tube, have attained commercial importance in relay, thermostat and other devices. When such a device is in one operating position the mercury container is tilted to establish an electrical circuit by causing a ilow of mercury to bridge electrodes located near one end of the container, while in another operating position the circuit through these electrodes is interrupted due to the tilting of the container in the opposite direction to cause flow of the mercury away from the electrodes. Where such mercury switches are incorporated in devices that provide for a relatively large angular movement of the tiltable container, no complications are likely to be encountered. But such mercury switches possess advantages which render them desirable for use in other classes of devices, as thermoelectric and electronic relay devices, wherein the energy input is so limited that only a relatively small angular movement of the container may be obtained. In the latter type of device proper electrical circuit control by the mercury switch under the operating conditions of limited energy input requires accurate positioning of the switch, as otherwise it is possible for the device to be so installed that the maximum amount of angular movement of the container obtainable from its actuating means operating on limited energy input is insuillclent to effect the desired flow of mercury out of and into contact with the electrodes. Also, in sensitive thermostatic devices suitable for operation over a narrow temperature range, as by bimetallic or vapor pressure means, substantially accurate physical positioning of the device, and hence of the tiltable mercury switch, is also necessary to insure agreement between the actual temperature control point of the device and the nominal temperature control point indicated on the adjustable pointer and scale arrangement of the device.

It is an object of this invention to avoid the difllculties above referred to and provide an improved mercury switch of the tiltable container type wherein the switch is rendered ineilective if it is not properly installed.

Another object of this invention is to provide a mercury switch of the type characterized which is particularly sensitive for use with actuating devices having available onlyrelatively small energy for operating the switch.

Another object of this invention is to provide an improved mercury switch of the tiltable container type, such as may be operated by a suitable relay or thermostat, having connected therewith a second mercury switch-which requires the proper installation of the switch as a unit before the circuit can be controlled through said first named or main switch.

Another object of this invention is to provide an improved mercury switch of the type last characterized wherein the second referred to mercury switch is of improved construction so as to afford increased sensitiveness.

Another object of this invention is to provide an improved mercury switch of the type hereinabove characterized which isA simple in construction and certain in operation.

Other objects will appear as the description of the invention proceeds.

Stated generally, the improved mercury switch of the present invention includes a main mercury switch of any suitable construction and operable i by any suitable device, such as a relay or a thermostat, associated with a frame or housing or other suitable support that has rigidly attached thereto a second mercury switch which is electrically connected with the first named switch and so constructed that, only when the mercury in the second named switch is in a central position, can the main mercury switch, actuated by its actuating device, control the electrical circuit. Thus, failure to install the mercury switch as a unit in proper position results in the controlling of the electrical circuit at the second referred to mercury switch, which is sometimes herein referred to as an alignment responsive switch, and as the latter switch is electrically connected with the main mercury switch, control of the electrical circuit is assumed by the alignment responsive switch rather than by the main switch. Therefore, the inoperativeness of the device as a whole calls attention to the fact that an improper installation has been made.

The invention is capable of receiving a variety of mechanical expressions one of which has been illustrated on the accompanying drawing, and therefore it is to be expressly understood that the drawing is for purposes of illustration only and is not to be construed as a definition of the limits of the invention, reference being had to the appended claims for that purpose.

In the drawing, which is a somewhat schematic elevation view, partially in section, of a mercury.

switch embodying the invention, lil designates any suitable actuating device for a mercury switch, here shown as in the form of a relay comprising an electromagnet II and a movable core member I2 which is operatively connected, as by a pivot I3, to a plate I4 pvotally mounted at I5 in any suitable way and on any suitable support. The electromagnet II is shown as provided with leads I6 for connection to any suitable source of electrical energy.

Mounted on the plate I4 in any suitable way, as by a clip Il, is a main mercury switch of the tiltable type and which also may be of any suitable construction, being shown as in the iormof a tube I8 having a pair of electrodes i9 and 2li projecting into suitable wells ZI formed in the wall of the tube I8 and also including-a pool` of mercury 22. When the mercury 22 is at one end of the tube IB as illustrated in the drawing, the electrodes I9 and 2li are bridged thereby and the circuit through the electrodes is closed. The position of the parts as show-n4 in the drawing corresponds. to the casewhere the leads I' are energized and the resultant downward movement of the coremember I2, causes plate I4 to. be turned ina clockwise direction about its pivot I to establish a closed electrical 4circuit through said electrodes Ill and 20. Upon cle-energizing the leads I5, the core member I2` under the action of a spring or other suitable means is moved upwardly as Viewed in the drawing to tilt the tube IIJ-in a counterclockwise direction about its pivot I5, whereby the mercury 22 moves away from the electrodes I9- and 20 tointerrupt the electrical circuit therethrough.

The details of the tubular mercury switch as so far described, and also the. relay for operatingthe same, constitute nopart of the, present invention, as any suitable switch and actuating means therefor maybe employed. Similarly, the pivotal mounting plate I4 forl the tiltable. switch member I8 may be constructed in any other-suitable way-for example, it may be: counterbalanced so asf to compensate; for the unbalance arising from the construction.illustrated;

In conformity with the present inventiony a second mercury switch, or alignment responsive switch, having its axis in suitable relationshiptoV theaxis about which switch I8: moves is rigidly mounted on the. before mentioned support, here shown as. a frame. or housing. 23, this second switch. being electrically connected with thev mercury switch i8. As illustrated somewhat dia.- grammatically in the drawing, thissecond mercury switch includes a. suitable envelope 3&1, preferably in the form of a tube, and a pair of sealing members 3|, disposed intermediateI the ends of, the-,tube 30 so as to: bel relatively remote therefrom. Sea-ling membersll carry probe-like members 32V and, 33v suitably sealed. into said envelope, said members 32, 33` preferably dependingY into the tube soas to project downwardly across the major portionof its diameter and to be in position to pass throughthe surface or" a mercury pool Srl. Mercury pool 34 is. of suitable size and so disposed within the tube 30v that it bridges the members 32 and 33 when the tube 30 is insubstantially ahorizontal position. In the illustrated embodiment, members 32, 33 are made a part of theelectrical circuit and serve as electrodes which cooperate with mercury pool 34 so that when tube 3i) is in substantially ahorizontal position a continuous electrical path is provided. Other physical arrangementsiof the alignment responsive switch. 3.0i may be. employed if desired,

but the illustrated arrangement is preferred inasmuch as greater sensitivity to angular displacement is obtained where, as shown, the electrodes are positioned medianly of the tube 30 so as to be not only adjacent to each other but also relatively remote from the ends of the tube 30, depending into a position wherein their extremities are submerged in the pool of mercury 34. Tube 3G may be rigidly mounted on the frame or casing- 213 in any suitable way as by a pair of clips 35.

Any suitable means may be provided for connecting the probe-like members or electrodes 32 and 33 in series with the electrodes I9 and 2U. [is illustrated, terminal blocks 40, 4I and 42 oi any suitable construction are mounted on the frame or housing 23 in any suitable way, and a iexible connection 43 is provided between the electrode I9 and the terminal block 40, a flexible connection 44 is provided between the electrode 2d and the terminal block 4I, and connectors as wires 45 and 4E, which may be flexible or rigid, are provided between the terminal block and electrode 32 and between the terminal block t2y and the electrode 33, respectively. The terminal blocks il and 42 also have any suitable provision for attaching thereto at 41 and 48 the leads from the circuit which is to be controlled by the switch I8.

The complete electrical circuit to be controlled by switch I8 therefore extends from input lead connection 4"! on terminal block 4I through flexible connection 44, electrode 2D, mercury pool 2v2,v electrode IS, flexible connection 43, teminal block: til, wire 45, electrode 32, mercury pool 34, electrode wire IE6 and back to the other input connection 48 on terminal blockv 42. When the frame or housing 23 is properly installed so that the tube` 30. is in a substantially horizontal position the circuit from the terminal blocks 4I and 42 to. the electrodes I9 and 2l) is complete through the electrodes 32 andk 33 by means of the mercury pool 34, Thereby the opening and closing. of said circuit may be` effected by the operation of the mercury switch I8 under the control of the relay I0. On the other hand, if the unit is not installed properly, so that the tube 30 is not in a substantially horizontal position, the circuit through the electrodes 32 and 33 is interrupted by the mercuryV pool 34 moving to one end or the other of the tube 3E). Thereby the circuit is broken between the terminal block 4,2 and the electrode I9. Under these conditions the mercury switch I8 is rendered inoperative notwithstanding energizationv and de-energization of the relay I0, so that warning is given that the installation is improper and appropriate correction must be made.

In general, the operating characteristics of the relay, thermostat or other actuating device ID-toget-her with its associated mercury switch I8- and the operating characteristics of the alignment responsive switch must be coordinated to assure that under conditions of improper horizontal po-v sitioning of the alignment responsive switch` and hence housing 23 the electrical circuit between the terminals on blocks 4I, 42 will be controlled by the alignment responsive switch rather than by the main switch I8. Thus, for example, inthe embodiment as illustrated in the drawing the angular displacement between the horizontal and the maize or break positions of the switch I8'v eiected by the relay I is, as a matter of practice, made greater than the angular displacement from thel horizontal required to liust make or break the circuit through the electrodes IS and 2i), the additional angular displacement being provided as a factor oi' safety to nullify slight errors of installation. However, as will be apparent, errors of installation exceeding the fore-A going excess capacity for angular displacementA will result in theactuating vdevice I being unable to move the switch I8 Vthrough an angle sumcient to properly make or break the circuit through the electrodes I9 'and'20. vTo provide the safety fea-I,

ture of the present invention the angular displacement at the horizontal tube 30 required to break the circuit between the electrodes 32 and 33 must not exceed the difference in angular displacement between the actual displacement from the horizontal of which switch I8 is capable and the minimum displacement of switch I8 required to make and to'break the circuit whichever diierence is smaller. If the minimum displacement of switch I8 from its closed position required to open the circuit through its yelectrodes is different from the minimum displacement from its open position required to close said circuit, the angular displacement from the horizontal of the switch 30 required to break the circuit through the electrodes 32 and 33 must not exceed'the smaller of the differences in angular displacement between the total actual displacement of the switch I8 effected by the relay I0 and the minimum displacements'of said switch required to just open and just close the circuit, i.`e., to just reverse the circuit condition through switch I8 from the open and closed positions.

When the device shown in the drawing is installed improperly the alignment responsive switch will cause the electrical circuit conditions between terminal blocks 4I and 42 to assume the condition that would normally obtain with proper alignment when electromagnetic device II is de-energized. Thus, under normal conditions de-energizing device I I causes the circuit between terminal blocks 4I and 42 to be open. Therefore, the alignment responsive switch 30 is so arranged as to open the circuit between the terminal blocks 4I, 42 under conditions of improper alignment of the device.

I am aware that leveling switches have heretofore been proposed which include a pair of contiguous electrodes in a common well or closely adjacent wells at one end of a container, but experience has demonstrated that such switches lack the sensitivity required for providing the before described safety feature where the mercury switch to be controlled is actuated by a relay, thermostat or other actuating device for which only relatively small energy is available.

It will therefore be perceived that the present invention provides an improved mercury switch of the tiltable type which has in circuit therewith a mercury switch of high sensitivity so that slight displacement of the switch as a unit for its proper position will result in rendering the main mercury switch ineffective as a circuit controlling member and thereby give warning that the installation is improper. Thereby mercury switches of the tilting type may be used satisfactorily with relays, thermostats and other actuating devices notwithstanding that the energy available is quite limited, whereby tiltable mercury switches may be used with such devices without the diiiiculties heretofore encountered in assuring proper installation in order that such actuating devices shall satisfactorily effect the opening and closing of the circuit to be controlled.

While the embodiment of the invention illustrated on the drawing has been described with considerable particularity, it is to be expressly understood that the invention is not limited thereto, as the same is capable of receiving a variety of other expressions as will now be apparent to those skilled in the art. While a particular mercury switch of the tilting type, acting as a main switch, and a particular electromagnetically operated device functioning as a relay when associated therewith, have been illustrated and described by way of exemplifying the embodiment and operation of the present invention, it is to be expressly understood that the invention is not limited thereto as tiltable mercury switches of other constructions, and other forms of actuating devices therefor, may be used in embodying the present invention without departing from the spirit thereof. Also, while a preferred form of alignment responsive switch has been described with considerable detail, such alignment responsive switches may take other forms without departing from the broader aspects of this invention as will now be apparent to those skilled in the art. Reference is therefore to be had to the claims hereto appended for a definition of the invention.

What is claimed is:

1. In a device of the character embodying two mercury switches connected in series in a circuit to be controlled, the combination of a common switch support normally occupying a fixed position in space, a first mercury switch movably mounted on said support, a controlling circuit, means responsive to changes in the electrical energy conditions in said controlling circuit for repeatedly moving said iirst switch between open and closed positions, and a second mercury switch connected in series with said iirst switch and fixedly mounted on said support and held in a fixed position in space when said first switch. is moved, said second switch including a tubular envelope, a mercury pool in said envelope and a pair of electrodes positioned adjacent one another near the middle of said envelope, the circuit through said electrodes being closed continuously by said mercury pool when said support is properly installed with the envelope of said second switch in a horizontal position, and being open continuously when said support is installed improperly with the envelope oi' said second switch misaligned with respect to the horizontal.

2. In a switch device of the character described, a support adapted to occupy a fixed position in space, a first mercury switch tiltably mounted on said support having a pair of electrodes connectable to a circuit to be controlled, means including a relay responsive to the electrical energy conditions in a controlling circuit for repeatedly tilting said rst switch back and forth between one position of rest wherein the circuit through said elect-rode is closed by the mercury of said switch and a second position of rest wherein the circuit through said electrodes is open. and a second mercury switch having electrodes connected in series with the electrodes of said first switch and iixedly mounted on said support. said second switch including a pool of mercury which continuously completes the circuit through the electrodes thereof when said support occupies' the desired fixed position in space but flows away from said electrodes and opens said circuit when the support is angularly displaced with respect to said desired position.

3. A switch device as claimed in claim 2 wherein the desired fixed position in space of said support is such as to maintain the second switch in amappmximatelyrhorizontaliposition; am'Lwherev in 7 mdf, second switch;` is? so4 v constructedJ andarranged that4 it-v willcpen; the; circuitthroughf the -V electrodesz; upon; arr angular; displacement there.-

o! withutespect to thehorizontal of. less magnitude-than the; smaller of theangular differencesl between: the; totalA actual angular displacement of said. rst switch when tiltedfromone of itsfrest` positions to theaother" and the minimum angular displacementsf of said: rst `switch from said: rest A positions.rrequired'. to just reverse'y the circuit` condition through its electrodes.

4; In a switchidevicezofsthe-charactervdescribed,.

asupport adapted tooccupy aiixed, position in` space;` a rst mercury switch comprisingg a. tubular envelopetiltably mountedon saidsupport, a

mercury-pool. in said envelope and a; pair of.. electrodes connectable.- to:- a. circuit to be com1 trailed, means `responsive tothe electrical energy conditions in: a controlling. circuit for. repeatedly tilting the envelope of vsaid rstswitch backV andA forth between one positiony of. rest4 wherein. the circuit., throught said electrodesis.. closed by the. mercury pool and a second position of rest wherein the circuit through said. electrodesy is. open, and a secondmercury switchxedly mounted on saicisupport andincluding. a. tubular envelope, a pair` of. electrodes positioned, adjacent onev an.- other near the middleof saidenvelope connected in series withtheelectrodes of said. rst switch and. armercury. pool for bridging said. electrodes.

8,. said1 mercury,v pool; continuomllill completing the circuit, through the electrodesA` of; said semmaiy switchl when. said:A supporti occupies thel desired.v nxed position infspace butowing aarwaygfroxri;snid-A electrodes and, opening said circuit when theu first switch when tilted from oneof, its sit-rest..

positions tothe other and the minimum angular:

g displacement of said. rst-switch from either'` o!Y saidk at-rest. positions required to just reversey the circuit: conditionY through its electrodes.l

PAUL L. ma.

REFERENCES CITED The following` references` are of. recordv in. the.. le oithispatent:

UNITED STATES PATENTS Number, Name Datel 1,676,791 Mailey July 10; 1928 1,871,177 Held Aug., 9, 1932 1,907,639 Young May 9.1933. 1,930,435 Walker Oct. 10, 1933 2.232.627 Olson Feb.. 18.'` 1941 

